This invention relates to a method and apparatus used in producing a feed product or premix and the product made by the method and, more particularly, to a process using co-drying to dry a mixture of krill hydrolysate and dry carrier or a mixture of krill hydrolysate, fish hydrolysate and dry carrier. The invention further relates to recovering enzymes from krill and, more particularly, to recovering enzymes from both freshly harvested and hydrolyzed krill. The invention further relates to utilising krill enzymes for removing protein from marine and biological wastes and, more particularly, for removing protein, chitin and other constitutents from crustacean and other marine wastes.
With the advent of increasing activity in aquaculture or fish farming in the early to mid-1980s, research has been ongoing into increasing productivity or growth rate and reducing the mortality rate of fish raised in aquaculture conditions since survival of such fish is important. One such factor relates to enhancing the nutritional value and palatability of feed used in raising such fish. In addition to the nutritional value, it is desirable to reduce the cost of feed to such fish since, typically, the feed totals approximately 40 to 50% of the cost of raising the fish. Such feed should be a high quality feed to meet the objectives of having high nutritional value to maximize growth and to reduce fish mortality.
The requirement for feed products in aquaculture is projected to grow substantially and, as a result, there is and will be pressure to obtain the necessary ingredients for fish food. The possibility of using zooplankton and, in particular, euphausiids, as a fish feed, appetizer or food product has been investigated and has been found to be possible and desirable, particularly as a feed product.
In addition, blends of krill hydrolysates and fish hydrolysates or any one of these with a dry carrier, can provide alternatives to fish meals in aquaculture and other animal feed diets. Euphausiids are a natural feed harvested directly from coastal waters and have a high nutritional value but, previously, the cost of harvesting and processing such zooplankton for a feed product has been prohibitively expensive.
As well, the questions of the availability of the biomass of such zooplankton and its harvesting, handling, storage and processing are parameters that must be investigated in order to determine whether the product would be appropriate as a feed product.
Through papers written by Fulton and other authors, the use of zooplankton as a food or feed product has been contemplated for some time. In particular, antarctic krill (Euphausia superba) for human consumption have been investigated, although relatively little work has been investigated related to aquaculture. The use of Euphausia pacifica in the coastal waters of British Columbia, Canada has been considered in relation to its use in aquaculture and other animal feeds.
It appears, from those investigations, that the necessary biomass is available in coastal waters. Previously, euphausiids have been used as a pet food ingredient and some aquaculture operators have used euphausiids as a feed product. The euphausiids were used for such purposes in a frozen form after being harvested and in some cases, the euphausiids were freeze dried following harvesting. This is an expensive procedure.
In processing feed products, it has typically been the case that the ingredients used in such feed products are heated to a high temperature around 100xc2x0 C. when the product is processed and dried. By heating the product to such a high temperature, it is believed that the enzymes and other proteins in the product are denatured. If, however, it is intended to utilize the product for early stage or juvenile aquaculture, which young fish have relatively undeveloped digestive systems, it is desirable that in some application, the euphausiid products maintain a certain proportion of enzymes which will assist the digestive process in juvenile and other life stages. If the theory that enzymes are advantageous in nutrition is correct, such destruction of the enzymes during the aforementioned drying process is disadvantageous.
It is also desirable to have a natural product, where the proteins are not denatured, available for early stage juvenile or larvae feed. In some previous products, exogenous enzymes have been added to the zooplankton mix. However, the addition of such enzymes is difficult to control and can result in a complete hydrolysis of the proteins to amino acids. The presence of free amino acids in the feed needs to be controlled since they can create an inferior product of substantially reduced value as a feed product.
It has been shown, surprisingly, that the degree of enzyme activity which results in determining the digestibility of a product, reaches a relatively constant value after a certain period of time in a natural product. Recent investigations conducted by the applicant have confirmed this characteristic for Euphausia pacifica. This characteristic was first discovered in relation to Euphausia superba by Kubota and Sakai in a report entitled xe2x80x9cAutolysis of Antarctic Krill Protein and Its Inactivation by Combined Effects of Temperature and pHxe2x80x9d, Transactions of the Tokyo University of Fisheries, number 2, page 53-63, March 1978. However, the antarctic krill study done by Messrs. Kubota and Sakai had the objective of limiting enzyme activity which was deleterious to obtaining a food as opposed to a feed product. Messrs. Kubota and Sakai wished to inhibit the enzymatic activity by certain processing techniques which they considered desirable when the product was intended as a food product.
An appropriate degree of hydrolysis is obtained during the digestion of the euphausiids. The approximate degree of hydrolysis will vary depending on the final application and it can be monitored by measuring the apparent viscosity in the final product. Further processing may then take place in order to make a useful product for commercial feed. Such processes may include adding acid to obtain an acid stabilized product concentrating fractionating or drying the product. A variety of drying techniques such as freeze drying, spray drying, or vacuum and air drying. Spray drying, as well as some other drying processes, however, are done at temperatures that will permanently inactivate the enzymes in the euphausiids which, as earlier mentioned, may be undesirable for aquaculture purposes although it is acceptable for purposes where the product is intended to be used as a carotenoid biopigment for coloring purposes in both feed and food products or as a source of protein, fatty acids, minerals or other nutrients.
According to one aspect of the invention, there is provided a method of producing a feed product comprising the steps of adding a predetermined quantity of krill hydrolysate to a quantity of dry carrier to produce a mixture and co-drying said mixture to obtain an end product. The dry carrier may conveniently be a plant protein, dry krill, fish meal, byproduct meal or other dry ingredient suitable for inclusion in a diet.
According to a further aspect of the invention, there is provided a product produced by adding a predetermined quantity of krill hydrolysate to a quantity of liquid marine protein and a quantity of dry carrier to produce a mixture and co-drying said mixture.
According to a further aspect of the invention, there is provided a co-drying apparatus for drying a mixture of krill hydrolysate with or without an evaporator and liquid marine product and a dry carrier comprising a dryer for concentrating, mixing, agitating, heating and separating particles of said mixture.
According to still a further aspect of the invention, there is provided a method of obtaining an enzyme extract from a liquid krill hydrolysate comprising the steps of subjecting said hydrolysate to decanting and then to centrifugation to obtain a clarified liquid and further subjecting said clarified liquid to ultrafiltration using a membrane with a capacity to retain said enzymes having a molecular weight greater than 10,000 daltons and the product produced by the method.
According to still a further aspect of the invention, there is provided a method of obtaining an enzyme extract from fresh krill comprising the steps of squeezing said krill to obtain an aqueous extract and subjecting said aqueous extract to ultrafiltration with a membrane adapted to retain enzymes having molecular weights above 10,000 daltons and the product produced by the method.
According to still yet a further aspect of the invention, there is provided a method for removal of protein from non-stabilized or fresh crustacean shell wastes comprising grinding said crustacean wastes and water, transferring said product to a digester, adding a predetermined quantity of krill enzymes to said digester, subjecting said mixture to digestion for a predetermined time period at a predetermined temperature, dewatering said digested product to obtain a first portion being relatively enzymatically active and relatively high in protein and a second portion of shell material relatively high in chitin and low in protein.
According to still yet a further aspect of the invention, there is provided a method for removal of protein from acid stabilized shell wastes comprising grinding said crustacean wastes, transferring said small particulate size shell wastes to a digester, adding a predetermined quantity of krill enzymes to said digester, subjecting said mixture to digestion for a predetermined time period at a predetermined temperature, dewatering said digested product to obtain a first portion being relatively enzymatically active and relatively high in protein and a second portion of shell material relatively high in chitin and low in protein.